Short Circuit Laboratory

Short Circuit Laboratory (SCD)

The Short Circuit Laboratory has facilities to undertake tests for certification and development of low voltage switchgear and control gear and other power system apparatus. The laboratory has 50 MVA short circuit test capacity.

The main power source to carryout the test at short circuit lab is a 50 MVA 12 kV 50 Hz 3-phase Short circuit Generator coupled to a 3.3 kV, 750 kW slip-ring type induction motor. A DC generator is also coupled on the short-circuit generator shaft for excitation.

The S.C. generator is a salient pole machine with two windings per phase, which can be connected in either series or in parallel and also in star or delta connections as per the requirement. With this, four types of ratings viz., 3.46, 6.0, 6.93 and 12 kV supplying a short circuit currents of 8.34, 4.82, 4.17 and 2.41 kA respectively can be achieved. Along with the generator there are two 50 MVA Short-circuit Transformers to step down the voltage to the value required. One of the transformers is 12kV/415V and a Short circuit current of 50 kA rms can be achieved at 456 Vrms recovery voltage. The other has taps both on the primary and the secondary. With that it is possible to test equipment up to 866V rating. This transformer is generally employed for testing MCBs, switches of all kinds and certain tests on fuse. The generator and transformers are specially designed to withstand repeated short circuits.

Apart from these, the lab has 12kV, 1250A, 40kA, breaking capacity of Vacuum Circuit Breakers which is used as the master breaker and a high-speed Make-switch with a point-on voltage wave closing facility. Resistor banks and Reactor (air-core) banks are available for adjusting the test current, power factor of the test circuit both on the source and load sides. The laboratory has also an ON-LINE testing facility.

D.C test facility is also available with which tests at 30kA.dc/600V & 3kA.dc/600V can be carried out. A 30kA d.c. for 3.0 seconds short-time currents test facility is also available at the lab.

The laboratory is equipped with modern digital measuring and recording systems. The high current measurements are made using non-inductive shunts (100kA, 10kA) and the voltages are measured using either resistive or capacitive voltage dividers or P.Ts. A digital waveform recorder with associated data acquisition system enables processing of the test data and preparation of test reports.

Testing & Certification :

Type tests and Routine tests on low voltage switchgears and control gears, distribution transformers up to 11kV class and other power system apparatus can be undertaken in the Short Circuit Laboratory as per the relevant Indian Standards (IS) and International specifications (IEC, BS, CSA, UL, ANSI, IEEE)

Research & Development activities:

The laboratory undertakes applied research and helps in the development of indigenous products, mainly on low voltage switchgears and control gears.

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